High cell density perfusion cultures has become the method of choice in in vitro animal cell cultivation for the production of numerous therapeutic proteins such as HBAg(hepatitis B surface antigan), tPA (tissue plasminogen activator), etc. which are of great commercial value. The major advantage of perfusion compared with the other popular types of cell cultures (e.g. batch or fed-batch) is the much higher productivity per culture volume. This is owing to the very high cell densities (10-fold or higher) that can be achieved.
High cell densities can only be attained with the use of an efficient cell filtration device, located in the effluent stream of the bioreactor. The role of that device is to prevent the entrainment of the viable cells outside of the bioreactor during the replenishment of the spent culture medium with fresh medium. A successful cell filter should be able to fulfil as many as possible of the following requirements: (1) Minimal cell damage or effect on cell growth and productivity. (2) Selective retention of the viable cells only. Nonviable cells must be removed from the culture, since they lyse and release undesirable components into the culture environment. (3) High cell retention efficiency. (4) Uninterrupted operation for long periods of cultivation. (5) Low energy consumption. (6) Simplicity in operation and maintenance. (7) Scale-up capabilities for large scale production units. (8) Compact structure. (9) Cost effectiveness.